Small-angle drill-hole whipstock



Jan. 29, 1963 D. E. NIELSEN ETAL SMALL-ANGLE DRILL-HOLE WHIPSTOCK Filed May 5, 1961 INVENTORS DALE E. NIELSEN JAMES L. OLSEN BY WALTER PBENNETT F ATTORNEY tats ilit

The present invention relates, generally, to drill hole whipstock devices and, in particular, to a small angle drill hole whipstock for use in drilling extremely accurate, line-of-sight test holes as required in underground nuclear test shots.

Whipstock devices are most commonly employed in the field of oil drilling or water well drilling. In the course of drilling water or oil wells, there are numerous instances where directional hole drilling is, not only desirable, but necessary. Such directional drilling, for purposes of simplicity, may be divided into two basic categories. The first category is the process of directional drilling for the purpose of reaching an exact, predetermined location, wherein the path taken, en route, is relatively unimportant. The second category is directional drilling where the hole may or may not be drilled to reach an exact location, but, wherein the path must substantially follow a predetermined route. Therefore, directional drilling, as performed with respect to oil recovcry and as is generally thought of in the art, consists of drilling a new upper portion of hole (ranging from 500- 10,000+ feet deep) and thereafter, using a whipstock assembly to kick the hole off at the desired angle or angles. When employing the whipstock in such directional drilling, each setting thereof changes the direction of the main hole on the order of from 37. Thus, whipstocks are generally used to force the bit away from a relatively straight path to follow a slanted path therefrom, with the intentions of reaching a predetermined location; where such paths may possibly attain a final angle approaching 90 with the main hole. On the other hand, when a hole deviates from a desired path in oil well drilling, it is again advantageous to use the whipstock to angle the bit back to the desired path. It becomes apparent that in the course of drilling this latter hole, there may be numerous deviations and whipstock corrections resulting along the hole with many doglegs or S shaped portions along its length.

Since the advent of underground nuclear explosion tests, there has resulted a further use for drilling apparatus and whipstocks in particular. That is, in the field of undground explosive studies, there is need for a combination of the above first and second categories of directional hole drilling. In drilling a line-of-sight hole for obtaining results of test shots an extremely straight lineof-sight hole must be drilled from the point of vantage to an exact point of detonation. In this latter type of directional hole, it is necessary to not only reach a particular location, but to take an exact path en route. Therefore, after preparatory calculations pertinent to the route of the path taken by the drill bit has been performed, the drilling apparatus available must be capable of performing the drilling operation with the exacting accuracies necessary. Any slight deviation of the hole must be corrected immediately upon its discovery to prevent the resulting doglegs of previous mention. In the attempt to drill such line-of-sight holes it was found that conventional whipstocks were not capable of correcting hole deviation of less than /z.

The present invention, therefore, is an advance over the prior art in that it makes possible the correction of a directional, straight hole which has deviated a very slight angle such as, for example, /s or A". Such an Patented Jan. 29, 1963 'i' 4'; advantage is not only of special importance in drilling line-of-sight holes for underground nuclear explosion studies, but is also of general interest for application in the field of oil and Water well exploration. The invention, furthermore, is easily oriented and permits such small angle corrections in drill hole direction with a minimum of drill bit binding, such as would be experienced if an attempt were made to merely scale down the present day type of whipstocks to permit their handling such small angle requirements. The absence of binding in the presentinvention is due primarily to the employment of a cylindrical member as guide means for the bit. It is to be noted that the invention is not limited to the particular application of straightening crooked holes, but may also be used in the same manner as any other prior art whipstock for drilling a deflected directional hole.

Therefore, it is an object of the present invention to provide a drill hole whipstock for correcting small angle hole deviation when drilling a highly directional hole.

It is another object of the present invention to provicle a whipstock capable of correcting the direction of drill hole a very small angle with a minimum of binding of the drill bit.

It is still another object of the present invention to provide a whipstock capable of small angle hole correction when drilling line-of-sight horizontal or vertical holes.

Other objects and advantages will be apparent in the following description and claims considered together with the accompanying drawing, wherein the single FIGURE shows a broken out perspective view of the preferred embodiment of the present invention as employed in a drill hole.

Referring now to the drawing, there is shown a small angle drill hole whipstock 11 as set at the bottom of a drill hole 12 to either correct or deviate, as desired, said drill hole. The whipstock 11 comprises a main structural, hollow cylinder 13 constructed for example, from a length of well casing of the desired size and weight. A whipstock seating wedge-spike 14 is preferably welded onto the lower end of the main cylinder 13 to permit firmly setting the whipstock in the desired orientation within the drill hole 12 to prevent rotation during operation thereof. The wedge-spik 14 further functions as a spacer to hold the respective end of the cylinder 13 away from the base hole wall. The amount of deflection or deviation imparted to the drill bit by the whipstock 11 is determined, primarily, by the thickness of the wedge-spike 14 and a wedge shaped segment 16 mounted on the cylinder, preferably by welding. The wedge shaped segment 16 is disposed with its sharp edge downwardly and its blunt edge flush with the outer circumference above the upper end of the cylinder 13 and circumferentially disposed 180 from the position of the wedge-spike 14 on the cylinder. A drill stem 17 and drill bit 18, as employed in conventional directional drilling, are secured to the whipstock 11 by two shear pins 19, thereby permitting the whipstock to be fed into the drill hole 12, while simultaneously maintaining the orientation desired for the whipstock. Such shear pins 19 are oppositely disposed on a diameter of the cylinder 13 and circumferentially disposed from the Wedge shaped segment 16 and Wedge-spike 14.

In operation, at such time as the whipstock 11 is lowered to the bottom of the hole 12, weight is applied thereto to set the whipstock by means of forcing wedgespike 14 into the hole bottom and immediately thereafter to shear the pin 19, thus freeing the bit from the whipstock. As the drill stem and bit are advanced through the slightly angled whipstock, the bit which fits snugly within the confining walls of cylinder 13 is forced to deviate along the angle thereof, herein shown as angle theta,

length, the angle of the subject Wh'ipstock increases ac- 'cordingly.

The Whipstock, as in the prior art, may be either an expendable or'a recoverable type. The expendable whipstock is constructed substantially as herein set forth in the description, where the drill bit 18 may be withdrawn after the whips-took is used and the deviation of the hole is achieved. When an expendable whipstock is employed,

the bit is Withdrawn, leaving the whipstock in the drill hole. The second or recoverable type of whipstock is preferred here and is constructed with a demountable ring 21 disposed at the upper end, and Within the circumference of, said cylinder 13, thereby reducing the inside diameterof such upper end of cylinder 13. As the drill stem 17 and bit 18 are withdrawn after the Whipstock operation, the bit shoulders against the ring 21 and the whipstock 11 is withdrawn from the drill hole 12, therewith.

While the invention has been disclosed, herein,"with res'pe'ct to a single preferred embodiment, it will be apparent that numerous variations and modifications may be made within the spirit and scope of the invention and, thus, it is not intended to limit the invention except by the terms of the following claims.

What is claimed is: p

1. A small angle drill hole whipstock including a directional drill stem and directional drill bit comprising a hollow cylinder, spike means rigidly secured to the outer circumference of one end of said cylinder to engage the bottom of a drill hole and space the cylinder from the side wall of the hole, wedge means secured to the outer circumference of the other end of said cylinder at a circumferential position separated 180 from said spike means position, and pin means for securing said cylinder in concentric relation to said directional drill bit wherein application of force by means of said drill stem sets said whipstock and thereafter shears said pins to separate the directional drill bit from the cylinder.

2. A whipstockincluding a directional drill stem and directional drill bit for deviating a drill hole a very small angle comprising a hollow cylinder, 'a Whipstock seating spike extending-from one end of the wallet said cylinder, said Whipstook seating spike extending a predetermined radial thickness outwardly from said outer surface of said cylinder, a wedge shaped segment secured to the outer circumference of the other end of said cylinder at a position separated l from the circumferential position of said spike and With the sharp end of said segment pointing toward the spike end of the cylinder, said segment and seating spike having a radially extending thickness in relation to the "length of said cylinder to cause a skewing of from /8 to 1 to said cylinder upon setting same, and pin means disposed between said bit and said cylinder in spatial relation'to said spike and segment for securing said cylinder to said' drill bit and stem in nonrotatable relation to-thereby orient and set the whipstockin a drill hole wherein the application of force to said drill stem and bit sets said whipstock and thereafter shears said pin means to allow said bit to follow the inside wall of the cylinder into the formation.

References Cited in the file of this patent UNITED sTATEs PATENTS 

1. A SMALL ANGLE DRILL HOLE WHIPSTOCK INCLUDING A DIRECTIONAL DRILL STEM AND DIRECTIONAL DRILL BIT COMPRISING A HOLLOW CYLINDER, SPIKE MEANS RIGIDLY SECURED TO THE OUTER CIRCUMFERNCE OF ONE END OF SAID CYLINDER TO ENGAGE THE BOTTOM OF A DRILL HOLE AND SPACE THE CYLINDER FROM THE SIDE WALL OF THE HOLE, WEDGE MEANS SECURED TO THE OUTER CIRCUMFERENCE OF THE OTHER END OF SAID CYLINDER AT A CIRCUMFERENTIAL POSITION SEPARATED 180* FROM SAID SPIKE MEANS POSITION, AND PIN MEANS FOR SECURING SAID CYLINDER IN CONCENTRIC RELATION TO SAID DIRECTIONAL DRILL BIT WHEREIN APPLICATION OF FORCE BY MEANS OF SAID DRILL STEM SETS SAID WHIPSTOCK AND THEREAFTER SHEARS SAID PINS TO SEPARATE THE DIRECTIONAL DRILL BIT FROM THE CYLINDER. 